1. Field of the Invention
This invention relates to the testing of sealed containers having an internal pressure greater than atmospheric and, more specifically, relates to an apparatus and method for such testing which is capable of establishing carefully monitored, predetermined internal pressures within the container tested.
2. Description of the Prior Art
It has been known to provide tests of the security of sealed containers having internal pressures greater than atmospheric. Such needs have been particularly important in connection with packages for foods and beverages. For example, with respect to soft drinks, an internal pressure of about 150 psi may be encountered and, with respect to beer, a pressure of about 100 psi is generally encountered. The premature, undesired failure of the package to effectively maintain the sealed relationship cannot only result in loss of product and spoilage thereof, but also can create a safety hazard. For example, there have been instances wherein bottle closures have been projected through the air with an explosive type action resulting in injury to the person hit by the same.
As a result of increasing concern for not only minimizing, but totally eliminating all instances of human injury as a result of such accidents, convenient, efficient and reliable set procedures have been needed.
With respect to bottle closures, one known means for testing the security of a particular closure on a particular bottle involves the cumbersome procedure of cutting the bottle with the closure intact at a position below the closure. The bottle portion with closure in place was then mounted upon a suitable fixture which was in communication with a source of pressurized fluid such as air. The pressure was progressively increased until such time as closure failure occurred and the pressure at the point of failure was used as an indication of the effectiveness of closure securement and, to a certain extent, the integrity of the seal at different pressure levels. As a result of the need to destroy the package in order to perform such a test, such procedures have generally been regarded as not only being cumbersome and inefficient, but also have failed to provide a test of the full package in its sealed condition.
Another known approach to pressure testing of particular bottle closures has involved the use of a metal fixture made to the dimensions of the particular bottle on which the closure was to be employed. The closure was sealed to the metal fixture and a test procedure similar to that employed in connection with the cut-off bottle described above was used. This approach eliminated the need for cutting a container into two parts, but perpetuated the other disadvantages set forth above. This approach also assumed that all the container sections would, in fact, have the idealized dimensions of the particular metal fixture. In view of the interrelationship between glass or plastic finish tolerances and the dimensions of the metal fixture, in some instances, such assumption was probably not warranted.
We previously have created a pressure testing apparatus for sealed containers which involved placing the container in an inverted position within an enclosure and introducing pressurized air into the container interior by means of a needle which was in communication with a source of pressurized fluid. The container was permitted to move upwardly responsive to the application of pressure sufficiently high to create seal or container failure and an overlying, generally conical member caught the upwardly moving container by frictionally engaging the same. Such system also contemplated the use of bottle holding fixtures which conform to portions of the bottle between the base and the neck thereof and, also, involved the need to bolt or otherwise firmly secure the bottle receiving housing lid so as to resist the upward thrust of the moving bottle. While the general concept of this approach showed promise, the time-consuming manner in which bottles were introduced and removed, the need to have a number of different sized fixtures in complimentary shape with respect to each bottle to be tested, the absence of ready access to the housing interior, the absence of feasibility in respect of use of the equipment for a wide range of types and sizes of containers and the absence of significant safety features which would preclude laboratory or plant personnel from being injured during use of the system, have resulted in limited use of these approaches.
There remains, therefore, a substantial need for an easily used, economical, rapid and reliable test apparatus and method for testing the pressure holding capacity of various types of containers in a system which provides the opportunity to test the precise product which will be going to the marketplace without the need to alter the same prior to testing.